It's a welcome sign of de-escalation in Europe's only ongoing war.
In eastern Ukraine, government forces and Russia-backed rebels exchanged 200 prisoners on Sunday (December 29).
The swap is part of a deal brokered earlier this month that aims to end the region's five-year conflict.
According to figures from officials of the Donetsk and Luhansk People's Republics – the two separatist governments in the rebel area – Ukraine turned over 124 people and the separatists freed 76.
Ukraine's government has been criticised for giving away too much. Some of the prisoners it released included five former members of the now-disbanded special police force – the Berkut – who had been charged with the killing of protesters in Kyiv's Maidan Square in 2014.
Global affairs analyst Michael Bociurkiw told Euronews the prisoner swap "definitely played into the hands of Vladimir Putin".
"I think this was deliberately done by Putin to sow more disunity in Ukraine. Zelensky is going to come under a lot of criticism for that handover," said Bociurkiw, former spokesman for the Ukrainian mission of the Organisation for Security and Co-operation in Europe (OSCE).
Paris peace summit
The exchange comes following a peace summit in Paris in early December that marked the first meeting between Ukrainian President Volodymyr Zelensky and Russian President Vladimir Putin.
The summit was one of the first tests for the comedian-turned president following his election last spring. Experts said that a prisoner swap could be possible after the meeting.
The 2014 conflict in eastern Ukraine broke out shortly after Russia annexed the peninsula of Crimea, in a move widely viewed as illegal in the international community.
Agreements to end the fighting in the Donbass region have largely failed.
Kyiv and Moscow swapped prisoners in September, including Ukrainian filmmaker Oleg Sentsov.
At the time, Zelensky said the exchange was the first step to ending the conflict in eastern Ukraine.